ZnCO3(s) -----heat--------> ZnO(s) +CO2(g)
Besides using carbon (coke) to reduce metal oxides to metals, sometimes displacement reactions can also be used. The highly reactive metals such as sodium, calcium, aluminium, etc., are used as reducing
agents because they can displace metals of lower reactivity from their compounds.
3MnO2(s) + 4Al(s) → 3Mn(l) + 2Al2O3(s) + Heat
The reaction of iron(III) oxide (Fe2O3) with aluminium is used to join railway tracks or cracked machine parts. This reaction is known as the thermit reaction.
Fe2O3(s) + 2Al(s) → 2Fe(l) + Al2O3(s) + Heat